While biomedical instrumentation experts have long appreciated the diagnostic and monitoring value of bioelectrical potentials originating from, for example, the heart of a patient victimized by a myocardial infarction, accurately receiving, transmitting and recording the small voltages involved has never been an easy matter. Clinicians, general practitioners and specialists are all very much aware of the frustrations attending faulty recordings caused by motion artifacts, spurious electrical signals, corrosion, poor electrolyte stability, high skin impedance, and the like.
What with man now taxing his strength and endurance more and more at supersonic speeds, in aerospace explorations and in excursions to ocean depths, significantly increased reliance is placed on monitoring equipment and under greatly differing conditions. It is getting more important, for example, to provide electrodes which are versatile and reliable and which may be used almost as effectively with an active subject as with an immobilized person. Not only must the electrode fastened to the subjects's body be firmly secured for proper and accurate functioning, but it is necessary that the quantity of interposed electrolyte be such that it uniformly coats a predetermined area of the skin. Furthermore, this uniformity must be maintained throughout the recordings.
Also, both the comfort of the subject and the avoidance of distortions in, for example, electrocardiograms require that the electrolyte or electrode assembly should not irritate the skin even during prolonged contact.
Of course, the electrolyte must be of such a nature and composition that when in contact with the electrode it is electrically stable, i.e., it should provide good performance, such as low and stable offset voltages and low impedance throughout its use. It should not deteriorate, dry up or deleteriously affect the electrode. Nor should it be so viscous as to fail to adequately penetrate the skin. In short, storage stability or good shelf-like are very desirable.
Obviously, some very stringent requisites are being placed on body electrodes of the type contemplated herein. The search persists for improved electrode assemblies, as is evident from the following references which are deemed of interest: U.S. Pat. Nos. 3,027,333; 3,048,549; 3,170,459, 3,265,638; 3,420,223; 3,487,827; 3,567,657; 3,590,810; 3,607,788; "Principles of Applied Biomedical Instrumentation", by L. A. Geddes & L. E. Baker, 1968, pp. 208-9 and 243-245.
U.S. Application Ser. Nos. 11,208 and 103,498, now U.S. 3,701,346 patented Oct. 31, 1972, described in detail electrode assemblies of the type contemplated herein, particularly the latter application which is incorporated herein by reference and teaches a pre-filled electrode assembly essentially as shown in the drawing of the instant application.
It is the primary object of the present invention to provide a very unique and versatile electrode/electrolyte assembly having extremely desirable properties, included among which are a accuracy and reliable bioelectrical conductance.